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Chemistry > C5 Chemical Changes > Flashcards

C5 Chemical Changes Flashcards

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1
Q

A salt

A

Compound formed during a neutralisation reaction when some or all hydrogen ions in an acid are replaced with metal ions or ammonium ions

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2
Q

Neutralisation reaction

A

When an acid and a base are added together they cancel each other out and form a neutral solution

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3
Q

How to make a salt by reacting a metal with an acid

A

Salt is formed by replacing hydrogen ions in the acid with metal ions or aluminum ions

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4
Q

The reaction between a metal and an acid

A

Metal + acid ——> salt + hydrogen

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5
Q

A salt formed between a metal and sulfuric acid or hydrochloric acid

A

Salt will be chloride if acid is hydrochloric acid

Salt will be sulphate if acid is sulphuric acid

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6
Q

Which species is oxidised and which is reduced
in a reaction

A

The species that loses electrons is oxidized

The species that gains electrons is reduced

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7
Q

The reaction between a metal oxide or metal hydroxide and an acid

A

Acid + metal oxide = corresponding salt + water

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8
Q

Why the reaction between a base and a dilute acid is a neutralisation reaction

A

If a base is added to an acidic solution the solution becomes less acidic and moves toward the middle of the pH scale

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9
Q

How alkalis are a subgroup of bases

A

An alkali is a water-soluble base

Bases which can be dissolved in water to furnish OH-ions

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10
Q

How to make a salt reacting a metal carbonate with a dilute acid

A

Dilute hydrochloric acid

Add powdered zinc carbonate to acid

Continue to add powder until excess amount

Filter mixture in beaker to remove excess zinc

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11
Q

What happens when ammonia react with acid

A

Formation of a salt of weak bases and strong acid

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12
Q

Balanced equation for neutralisation reaction

A

NaOH + HCl ————> NaCl + H2O

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13
Q

How to use universal indicator to classify as acidic or alkaline

A

Few drops of universal indicator solution is added to each substance at a time

The colour obtained is compared to pH chart to give pH of solution

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14
Q

pH scale

A

Measures how acidic or alkaline an object is

Lowest 0 highest 14

Pure water has pH 7

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15
Q

Alkali effect on solution

A

A base or an alkali takes up hydrogen ions

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16
Q

Example of alkali

A

Sodium hydroxide

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17
Q

Example of a neutral

A

Pure water

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18
Q

Example of a base

A

Copper oxide

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19
Q

Acidic chemical example

A

Hydrochloric acid

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20
Q

Relationship between alkalis and bases

A

Alkali is a base

A base that dissolves in water

Not all bases are alkali but all alkali is base

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21
Q

How the pH of a solution changes as acid or alkali is added

A

pH below 7 is acidic

pH above 7 is alkaline

Acid added = pH decreases

Alkali added = pH increases

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22
Q

Examples of strong acids

A

Hydrochloric acid (HCl)

Sulfuric acid (H2SO4)

Nitric acid (HNO3)

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23
Q

Examples of weak acids

A

Acetic acid

Citric acid

Carbonic acid

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24
Q

How an acid or alkali can be concentrated or dilute

A

By adding water to a concentrated acid or base, the solution is diluted

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25
Q

How an acid or alkali can be strong

A

A strong acid is one that’s nearly or completely ionised in water

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26
Q

How an acid or alkali can be weak

A

If it’s only partially ionised in water

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27
Q

How concentration of hydrogen ions relates to pH number

A

As concentration of hydrogen ions increase the pH decreases

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28
Q

Acid

A

A substance that produces hydrogen ions when dissolved in water

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29
Q

The lower the pH solution…

A

…the more acidic it is

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30
Q

The higher the pH solution…

A

…the more alkaline it is

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31
Q

Indicator

A

A dye that changes colour depending on whether it’s above or below a certain pH

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32
Q

Wide range indicator

A

Indicators which contain a mixture of dyes so gradually change colour over a broad range of pH

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33
Q

What are wide range indicators used for

A

Estimating the pH of a solution

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34
Q

Why is a pH probe more accurate than an indicator

A

When the probe is placed in solution you’re measuring the pH is given on a digital display as a numerical value

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35
Q

How does a pH probe work

A

Attached to a pH meter can be used to measure pH electronically

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36
Q

What substance do acids form in water

A

H+ ions

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37
Q

What substance do alkalis form in water

A

OH- ions

38
Q

Base

A

Substance with pH greater than 7

39
Q

Neutralisation

A

The reaction between acids and bases

40
Q

Neutralisation reaction word equation

A

Acid + base ——–> salt + water

41
Q

Neutralisation reaction symbol equation

A

H+(aq) + OH-(aq) ——> H2O(I)

42
Q

What happens when an acid neutralises a base

A

The products are neutral (they have a pH of 7)

43
Q

Use of titrations

A

Allow you to find out exactly how much acid is needed to neutralise a quantity of alkali

44
Q

Titration experiment

Steps 1-3

A

Using a pipette and pipette filter add a set volume pf alkali to conical flask

Use funnel to fill a burette with some acid of known concentration - make sure to do this below eye level

Record initial volume of acid in burette

45
Q

Titration experiment

4-6

A

Using burette add acid to alkali a bit at a time giving conical flask a regular swirl

Go slowly when you think the end-point is about to be reached

Indicator changes colour when all alkali is neutralised

Record final volume of acid in the burette and use it along with initial reading to calculate volume of acid used to neutralise alkali

46
Q

In titration experiment why do you need to use funnel to fill burette with acid

A

You don’t want to be looking up if some acid spills over

47
Q

How to increase accuracy of titration

A

You need several consistent readings

Repeat whole thing few times

48
Q

Universal indicator

A

Used to measure pH of a solution because it can turn a variety of colours

Each colour indicates a narrow range of pH values

49
Q

What is universal indicator made of

A

Mixture of different indicators changes from red to violet

50
Q

During titration when will you see colour change

A

At the end-point

51
Q

What colour is litmus indicator

A

Blue in alkali and red in acids

52
Q

What colour is phenolphthalein indicator

A

Pink in alkalis and colourless in acids

53
Q

What colour is methyl orange indicator

A

Yellow in alkalis and red in acids

54
Q

Reactvitiy series

A

List of metals in order of their reactivity towards other substances

55
Q

The reactvity series order

Top half

A

Potassium

Sodium

Lithium

Calcium

Magnesium

56
Q

The reactvity series order

Bottom half

A

Carbon

Zinc

Iron

Hydrogen

Copper

57
Q

How are metals reactivity determined by

A

How easily they lose electrons

58
Q

How to tell the speed of a reaction

A

Rate of which bubbles of hydrogen are given off

59
Q

How to investigate reactivity of metals

A

By measuring temperature change of the reaction with acid or water over a time period

60
Q

Metal reacts with water word equation

A

Metal + water ——> metal hydroxide + hydrogen

61
Q

Calcium hydroxide

A

Ca(OH)2

62
Q

Calcium reacts with water symbol equation

A

Ca + 2H2O ———> Ca(OH)2 + H2

63
Q

Name the metals which react with water

A

Potassium, sodium, lithium and calcium

64
Q

Name the metals which don’t react with water

A

Zinc, iron, copper

65
Q

Oxidation

A

Gain of oxygen

66
Q

Reduction

A

Loss of oxygen

67
Q

2Mg + O2 ——–> 2MgO

Which is oxidised

A

Magnsium is oxidised to make magnesium oxide

68
Q

2CuO + C ——> 2Cu + CO2

Which is reduced

A

Copper oxide is reduced to copper

69
Q

What do metals need to be extracted from their ores chemically by reduction

A

Carbon

70
Q

How are the metals higher than carbon extracted by

A

Electrolysis (expensive)

71
Q

How are the metals lower than carbon extracted by

A

Reduction using carbon

72
Q

Why are metals above and below carbon extracted differently

A

Carbon can only take oxygen away from metals which are less reactive than carbon

73
Q

How to extract very unreactive metals

A

They are in Earth’s form as the metal itself

74
Q

Is the ionisation of a weak acid reversible reaction or irreversible

A

Reversible reaction

75
Q

Equation of strong acid

A

HCl ———-> H+ + Cl-

76
Q

Equation of weak acid

A

CH3COOH ——\ H+ + CH3COO-
-—–

77
Q

How to increase rate of reaction of acid

A

If concentration of H+ ions is higher

78
Q

pH of an acid or alkali

A

A measure of concentration of H+ ions in solution

79
Q

What happens to concentration for every decrease of 1 on the pH

A

Concentration increases by a factor of 10

80
Q

What us the general rule for pH

A

-x
Factor H+ ion concentration changes by = 10

81
Q

Which pH is stronger when they have same concentration weak or strong acid

A

Weak acid has more pH than strong acid if same concentration

82
Q

What does concentration measure

A

How much acid there is in a certain volume of water

83
Q

Metal reacts with oxygen equation

A

Metal + oxygen → metal oxide

84
Q

Displacement reaction

A

When a more reactive element displaces a less reactive element from a compound

85
Q

Why a displacement reaction may occur

A

More reactive metal has stronger tendency to lose electrons and form positive ions than less reactive metal

86
Q

Example of displacement reactions using an ionic equation

A

Zn + CuSP4 ——> ZnSO4

87
Q

How to use reactivity series to determine whether a reaction between a metal and different metal salt would happen or not

A

A metal will displace another metal from its salt solution if more reactive than the metal in the salt

88
Q

How is carbon used to extract from an ore

A

Heating the metal oxide in the presence of the carbon

89
Q

How is hydrogen used to extract from an ore

A

By reacting hydrogen directly with iron ore, iron and water are produced in place of iron and CO2

90
Q

How are metals extracted

A

Electrolysis

91
Q

Ionic equation for reaction between an acid and alkali

A

H+ + OH- ———-> H2O

92
Q

Why are gold and silver found naturally as elements in Earth’s crust

A

Unreactive

Chemistry (9 decks)

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